Radio transmitter



Feb 11, 1947. c. P, CLARE RADIO TRANSMITTER Filed May 20, 1944 2Sheets-Sheet 1 Feb. l1, 1.947.

C. P. CLARE RADIO TRANSMITTER Filed May 20, 1944 2 Sheets-Sheet 2 N ma mM JTWH m ,lmllw @5 M `Patented Feb. 11, 1947 UNITED srATcs nanro'massi/narran Carl l. Clare, Arlington Heights, Ill., assignor to C. P.Clare and Co., Ghicago, Ell., a corporation of Illinois Application May20,` 1944, Serial No. 536,584

4 Claims.

My invention relates broadly to remote control systems and moreparticularly to a system for transmitting warning signals in remotecontrol systems. ,l

This application is a continuation in part of my application Serial No.373,173, filed January 4, 1941, now Patent 2,355,055, issued August 8,i944, for Electric relay system.

One of the objects of my invention is to provide an electric relaysystem for operation in a remote control system by which various circuitpermutations and combinations may be effected and in addition arepeating warning signal may be controlled by the relay system.

Another object of my invention is to provide a local and remote controlcircuit for a radio transmission system by which the radio transmittermay be operated from a remotely controlled location for transmitting awarning signal preceding a radio transmission by voice modulation orother means.

Still another object of my invention is to provide a remote controlsystem for radio signaling systems whereby composite signals may betransmitted over desired time sequences by a radio transmitter that isremotely controlled from a supervisor position.

A further object of my invention is to provide a control circuit for aremote control system capable of establishing three different circuitconditions over a control line by displacement of a control key orswitch to either of three selective positions.

Other and further obje-cts of my invention re.- side in an arrangementof electric relay system having means for controlling the operate andrelease time of the magnetic system of a relay system as set forth morefully in the speciiication hereinafter following by reference to theaccompa, .og drawings, in which:

Figure l is a schematic wiring diagram showing the remote control systemof my invention for distant control of a radio transmitter whereby awarning signal may be transmitted from the radio transmitter to signifythe commencement -of a broadcast followed by the desired broadcast indesired sequence; Fig. 2 schematically illustrates the circuit conditionat the controlling station when the control key or switch is manuallyheld in dial position; Fig. 3 schematically illustrates the circuitcondition when the control switch Vor key is moved to locking ringposition; Fig. 4 schematically shows the circuit condition when thecontrol switch or key is in locking neutral position; Fig. 5' shows acharacteristic curve for the electric relay system used in the remotecontrol system of my invention in which the electrical operating time ofthe relay system is regulated in accordance with the principles of myinvention; and 1Eig. 6 shows a characteristic curve in which both theelectrical and vmechanical characteristics of the relay system arecontrolled for securing the repeat signal operation required as awarning signal in the remote control system of my invention.

My invention provides a method of remote control for a radio broadcasttransmitter or other signalling system for transmitting a warning signalin advance of a broadcast. The system of my invention is particularlyapplicable in aircraft traffic control and navigation systems in whichvan operator in a remote position with respect to a transmitting groundstation desires to notify aircraft that a broadcast is about tocommence. The operator in the remote control station is provided with athree position switch or key having a manually actuated dial position, alocking ring position and a locking neutral position. The operator maymanually move the control switch to dial position and dial a particulardigit on the remote control mechanism at the control station and thenquickly shift the control switch or key to ring position and allow theswitch or key to remain locked in ring position and in accordance withthe system of my invention effect the transmission of warning signals ata rate of approximately eight per second on any selected audio tonefrequency such as 1,020 cycles. The warning signals at 1,020 cycles aretransmitted so long as the control operator allows the control key orswitch to remain in ring position, thereby advising the pilots ofaircraft that a broadcast is about to commence. The operator may thenshift the key or switch to neutral locking position and control themodulation circuit of the distant radio transmitter either by voice ortelegraph signals. The control switch or key is always ready for arepeat control operation, the important sequence being the movement ofthe control switch or key first to dial position for effecting aselection of the connection between the warning circuit and themodulation circuit of the radio transmitter. Such selection when onceestablished is not disturbed by quick movement of thfe control key orswitch to ring position because of the time relay characteristics of therelay circuits employed between the control circuit and the selecto-rapparatus and the almost innitesimal interruption of the controlcurrent. This method of transmission has proven highly effective in thetransmission of weather, emergency warnings, traffic, and otherinformation to aircraft in a particular area. However, my invention isnot limited to this particular application and is applicable tosignalling systems generally in which a calling signal of predeterminedcharacteristic is to be transmitted in advance of the signallingoperation. My invention also has application to the transmission ofsignals of particular tones for controlling of start-stop functions forthe motor circuits of facsimile and printing telegraph systems andforthe starting through audio frequency transformer I to the Y contactsof the control key I8 for controlling connections to the line system I3.The control key I8 is indicated generally as having a dial position I9and a ringing position 20. The dial switch control device at the remotecontrol station is indicated at I6.A The signalling circuitl isindicated at II having leads LI and L2 normally connected through key I8to the line I3. The operator at the remote control station by moving keyI8 to the dial position i9 and operating the dial I6 opens and closesthe circuit over line I 3 for transmitting impulses to the controlledstation. At the controlled station relay A--4 |96 follows these impulsesand through-its back contact I causes the motor magnet I0 throughintermediate relay B-4I96 to actuate the stepping switch 2 l22 thespecic number of steps corresponding to the impulses transmitted fromthe dial through any suitable range such as l', 2' 30. Relay B-4I96 anda cut-out relay D-4ISS are both of a slow release type. The reason forthe use of time delay feature in the circuit of my invention is toprevent opening of the contacts in the absence of a control current fora given time period for maintaining the circuit in operation. Theinnitesimal interruption of currentfrom source I4 in the control circuitupon movement of key I8 from dial position I9 to ring position 20 doesnot interfere with the maintenance of the selec- -tionA circuit becauseof the slow release action of relay 13-M96. The intermediate relayB-4I96 duetoits slow release action remains operated after its circuitis rst closed, thus holding its contactsZ-S closed. After the lastimpulse from the dial, relay -D-MQS, which operated on the first impulsefrom relay .Ia-M96, due to its slow release action remains operatedduring the series of impulses transmitted from the dial and restoresandcloses a circuit from positive on contact 2 Vof relay A-l I 96 to theprimary relay associated with the last stepping relay step. Relay A-4I96remains energized so long as key I8 remains in dial position after theseries of impulses has been-transmitted, in order to maintain theselected primary relay energized, or so long as key I8v remains lockedin ring `position for transmitting current from source I4 to the linecircuit. Y Thedial position of the control circuit is shown more clearlyin Fig. 2 while the ring positionof'the control circuit is shown moreclearly in Fig.r3.

Therneutral position for key I8 is shown in Figi. Key I Bis of the camlever type in which the movement ofthe lever to-which handle of key I8is attached functions to engage cam members connected with the leafsprings for moving the leaf springs to operating position.

In Fig. 2, for example, wherein the key lever is movedto dial positionthe lever arm connected with the operating handle of key I8 engages cams'associated withulever springs 66 and 6l which are connected to the linecircuit I3 serving to spread the leaf springs and move them to positionsin which they establish connection with contactsto winding I5 of thetransformer circuit and through dial switch i6 and resistance III tocontact 68 and leaf spring 66 returning to the opposite side of line I3.Leaf spring 66 is associated with pedestal insulator 1I which connectswith leaf spring 'I2 for simultaneously moving leaf spring I2. Leafspring 'l2 when shifted as shown in Fig. 2 establishes connection withcontact 'I3 which places warning lamp 14 in circuit with the powersupply source from winding I5 of the transformer circuit I 4 therebyindicating to the station operator that key I8 is in dial position.

In the position illustrated in Fig. 3 wherein the lever controlled byswitch handle I8 is moved to ring position, it will be observed thatleaf springs 65 and 67 have been restored to neutral position andestablish connection with contacts 'I4 and 'I5 respectively completingcircuits to the lever springs indicated at 'I8 and Tl. The movement ofkey I8 to the position illustrated in Fig. 3 results in displacement ofspring members 'I6 and "I7 to positions establishing connection withcontacts 'I8 and 'i9 in circuit with winding I5 of transformer circuit,I4. This results in transmitting current from source I4 to line I3 solong as key I8 remains in the position illustrated in Fig. 3.

When key I8 is restored to neutral position as illustrated in Fig. 4leaf springs 'IB and 'Il establish connection with contacts and 8Iconnected to the supervising line circuit through leads LI: and L2thereby establishing Sonnection with a. signalling circuit or amodulating circuit at the: radio transmitter indicated at 28. y 'Delayedaction relay B--MSB prevents any interference with the properfunctioning of the control system by prolonging the circuit continuityduring transition produced preparatory to control of the system bycurrent impulses transmitted from the control station.

The primary relay operates to close a circuit to the desired controlwhich is required, This control may be the closing of certain amplifiercircuits or other desired switching operations. In the particular systemillustrated, I have shown the broadcast transmitter as comprising amodulation system 29, an oscillator 3i, a power amplifier 32 and anantenna-ground system 33. A modulation control circuit 28 extends to themodulator 29 and a local microphone 34 is provided in this circuit forany local control which may be required. An audio frequency transformer21 has its secondary winding connected to modulation circuit 28 and itsprimary winding connected to the leaf springs 25 and 26 of the springpile-up 24 of the auxiliary relay 39, The contact springs 25 and 26 moveto either of two positions. In the upper position, contact springs and26 connect with contacts 35 and 3S which connect to the contacts il andIof the contact assembly 23 of relay B--4I96. In the opposite position,leaf springs 25 and 26 connect respectively with contacts 3'! and 38leading to the tone frequency source under control of the relay system42 of my invention. The relay 42 comprises the magnetic core 44, theoperating winding 43, the slow operate slug 45 for electricallycontrolling the operating time of the relay and the armature 4t pivotedat 4l. The armature 46 has an operating lever arm 4S integral therewithwhich controls the operation of the spring pile-up shown at 593. Thearmature 46 has the inertia device 48 attached thereto for mechanicallycontrolling the operating time of the relay. The spring pile-up 5tincludes leaf springs El, 52, 53, 5ft, 55 and 55. The leaf springs El-EZcarry contacts 5la and c2c. which are electrically connected in serieswith the control winding s3 and with the power source through contactspring liti and coacting contact di of auxiliary relay 39. The relay d2is thus self- 'interrupting through the cooperation of contacts 5 l a,and in the current path to the rela-y winding d3 at a rate of timedepending upon the coaction of the inertia of armature i6 due to theadded mass i8 and the iniiuence of the eddy current field produced byslug 45 upon the normal field of winding d3.

A suitable source of alternating current having a tone frequency, forexample, oi 1G20 cycles is connected at 5l to primary winding 58 oftransformer 59, whose secondary Winding 6E! is connected to leaf springsand 56 of spring pileup 5d. The movable contact springs 52 53 and 55 areinterconnected through bushings of insulation material indicated at iiiand 52 so that movement of lever arm @s moves leaf spring 52 to opencontacts 5to, and 52a, while leaf springs 53 and 55 move to positions inwhich contacts 53o and a. establish connection with contacts Ella and5ta, respectively, thus closing the circuit from secondary winding Silof transformer 59 to the contacts 3l and 38 of spring pile-up 24 ofauxiliary relay 3S. I have schematically illustrated the prima-ry relaysof the remote control system at E-ill and F-ls and the secondary relaysat Cif-ilse I have schematically shown the several contacts and leafsprings for the several re- ,l

lays and control apparatus at i, '2, 3, 4, 5, 6, l', 8 and 9 withpolarities indicated to aid in tracing the circuits of the controlsystem.

In the instant case assume that it is desired to broadcast a certainmessage. The operator moves key it dial position l and dials the digit 3which causes the stepping switch 2 i-ZZ to step to its third contactsand relay A-lsl to remain energized afterward. Relay D--Llll onrestoring after third impulse closes a circuit to primary relay 3.Primary relay 3 closes a circuit to the auxiliary relay 3Q whichtransfers the circuit from contacts 23 leading to the modulation channelthrough the primary of the broadcast transformer 2 to contacts 54% and55 on the weighted armature relay l2 of my invention. The circuit to thewinding of the weighted armature relay i2 is also closed by theauxiliary relay. 39 through spring it and contact 4l' and as previouslydescribed, the weighted armature relay l2 operates approximately eighttimes per second to cause a warning i020 cycle tone to be placed on themodulation circuit 23 of the broadcast station. rThis interrupted toneis held on the modulation circuit of the broadcast station as long asthe operator at the distant control station allows the key i5 to remainlocked in ring position as shown in Fig. 3. After this tone has beenheld on the desired length of time for transmitting the warning signalthe operator restores the key i5 to neutral position as shown moreclearly in Fig. l, and the stepping switch 2|-22 restores itself tonormal.

The control operator by using key i8 and dial l5 as before, then dialsthe broadcast number and the Stepping switch Zl-ZZ functions to operatethe primary and secondary relays to effect whatever functions theycontrol, with leaf springs 25-26 of Spring pile-up 24@ contacting thecontacts and 36 as shown in Fig. l, after which (ill key I8 is restoredto neutral as shown in Fig. 4 and the broadcast takes place. Thus amultiplicity of functions may be'controlled over the sameline circuit byselection through the stepping switch mechanism 2 l22. After the warningsignals have been transmitted as hereinbefore explained the operatorupon moving key i3 to neutral in effect places signaling circuit il insupervisory position through leads Ll and L2 to line I3 and throughcontacts 4--5 and i-'i and contacts 2li-25 and 3ds-26 to the modulationtransformer 2l of the modulation circuit 23 of the radio transmitter.Thus a microphone and power source connected to signaling circuit l1enables the radio transmitter to be voice modulated from the remotecontrol position. If a sending key and power source is connected tosignaling circuit Il or any other form of modulating means employed themodulation circuit 28 of the radio transmitter can be correspondinglycontrolled.

I have found the relay system of my invention very practical andsuccessful in operation. The mass added by Weight d8 provides themovable armature system with that amount of mechanical inertia whichwill coact with the electrical inluence introduced by slug l5 to enableoperating winding 43 while energized from a continuously applied sourceto cause the controlled circuit connected through sets of Contactsprings 53, 5d, 55 and 55 to alternately connect and disconnect a sourceof control potential tothe circuit to be controlled. The rate at whichthis control is applied is readily controllable by changing thecharacter of slug l5 and the effective mass 48.

Figs. 5 and 6 illustrate the efiect of the slug i5 and the weight i8 onthe movable armature. in Fig. 5 the curves illustrate the manner inwhich the flux density increases and decreases in the magnetic systemaccording to time where the flux builds up during the make period ofcontacts Sia and 52a and decreases to a condition where it commences toincrease again before the flux cycle through the magnetic parts has beencompleted. The iniuence of slug i5 in the eX- ample illustrated is suchthat the flux cycle increases through a time period represented by aunit of time while the decrease in flux takes place over a fourth of theincrease time. The self-interruption effected by the breaking of thecircuit through winding i3 by contacts elo and 52a produces a repetitionof alternate increases and decreases of the fiuX cycle as illustrated.in order to increase the rate of make and break of the spring pile-upsystem the mass t is added to armature it with the result shown in Fig.6. The time period for initial build-up of the inagnetic nur is now oneunit of time compared to a tenth of the time for decrease of flux. Theux cycle is not completed but repeats in a series of substantiallysaw-tooth curves as indicated until the controlling current is removed.During this period the spring pile-up assembly is being functionedthrough a series of rapid repeating strokes and impresses thecharacteristic tone frequency from source lil? upon the load circuit ormodulation circuit of the radio transmitter illustrated in Fig. l. Byproportioning the mass of the movable armature system and thearrangement of slug d5 in the field of winding @l5 a rate of make andbreak of, for example, eight times per second maybe obtained.

The composite system of control of my invention enables an operator atthe remote control station Il vtocontrol the operation of the radiotransmitter at the local control station i2 so that voice transmissionfrom the radio transmitter maybe preceded by a warning signal producedby operation of the recycling relay system which may :be controlledsequentially to connect the 1020 cycle tone to the modulation circuit ofthe transmitter through transformer system 2l. The modulation circuit ofthe transmitter may be controlled by the supervisor from the remotecontrol station for emitting the desired characteristic of signal andthe radio transmitter may also be locally controlled through microphone34 connected with the voice modulation circuit 28. The slow releaserelay B-Mt in the control system prevents opening of relay contacts inthe absence of a controlled current for a given time (period, therebymaintaining the system in operation. The interruption of the key controlcircuit i8 does not interfere with the maintenance of a selector circuitbecause of the slow release action of relay B-MQS.

I realize that various changes may be made in the relay arrangement andwhile I have described my invention in certain preferred embodiments, Idesire that it be understood that modifications may be made and I intendno limitation upon my invention other than may be imposed by the scopeof the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

l. A control system for a signal transmission system comprising atransmitting station including a signal transmission system having alocal voice modulation circuit, an audio frequency energy transmissionchannel connected with said local voice modulation circuit, a source ofalternating current, a mechanically recycling relay including anoperating winding, a movable armature and a multiplicity of contactscontrolled thereby, circuits interconnecting said source of alternatingcurrent and certain of said contacts, a remote control station includingan alternating current control source, a two-position control switch anda dialing switch,-a circuit interconnecting said control source, saiddialing switch and one position of said two-position control switch, asignalling circuit connected with the other position of saidtwo-position control switch, a line wire control circuit interconnectingsaid remote control station 'and said signal transmission system forselectively establishing connection between said rst mentioned source ofalternating current and said audioy frequency energy transmissionchannel and controlling the impression of said mst mentioned source ofalternating current upon said audio frequency transmission channel at arate determined by the operation of said mechanically recycling relayfor correspondingly controlling the emission of a sustained signal fromsaid signal transmission system through said local voice modulationcircuit.

2. A control system for a signal transmission system comprising atransmitting station including a signal transmission system having alocal voice modulation circuit, an audio frequency enengy transmissionchannel connected with said local voice modulation circuit, a source ofalternating current, a mechanically recycling relay including anoperating winding, a movable armature and a multiplicity of contactscontrolled thereby, circuits interconnecting said source of alternatingcurrent and certain of said contacts, a remote control station includingan alternating current control source, a two-position control switch anda dialing switch, a circuit interconnecting said control source, saiddialing switch and one position ci said two-position control switch, asignalling circuit connected with the other position of saidtwo-position control switch, a line wire control circuit interconnectingsaid remote control station and said signal transmission system forselectively establishing connectionV between said first mentioned sourceof alternating current and said audio frequency energy transmissionchannel and controlling the impression of said rst mentioned source ofalternating current upon said audio frequency transmission channel at arate determined by the operation of said mechanically recycling relayfor correspondingly controlling the emission of a sustained signal fromsaid signal transmission system through said local voice modulationcircuit, and means connected with said line wire control circuit fordelaying the opening of said circuit in the absence oi a controlledcurrent.

3. A remote control system comprising in combination a remote controlstation and a local control station, a line wire circuit interconnectingsaid stations, a controlling source at said remote control station, asignal transmitter at said local control station, a mechanicallyrecycling relay at said local control station, a source of a1- ternatingcurrent connected with said mechanically recycling relay, a voicemodulation circuit connected with said signal transmitter, and meansoperated from said remote control station for directly controlling saidvoice modulation circuit of said signal transmitter or conditioning saidmechanically recycling relay for periodically impressing the source ofalternating current at said local control sta-tionupon the voicemodulation circuit of said signal transmitter over a predetermined timeinterval.

4. A remote control system comprising a transmitting station including asignal transmission system having a local voice modulation circuit, anaudio frequency energy transmission channel connected with said localvoice modulation circuit, a mechanically recycling relay including anoperating winding, a movable armature and a multiplicity of contactscontrolled thereby, a tone frequency source connected with saidmultiplicity of contacts, means for completing a circuit between saidlocal Voice modulation circuit or between said local voice modulationcircuit and said audio frequency energy transmission channel, a controlstation, an audio frequency source and a signal circuit at said controlstation, and a selector switch at said control station for renderingeither said signalling circuit or said audio frequency source at saidcontrol station effective over said audio frequency energy transmissionchannel for selectively controlling the connection of said mechanicallyrecycling relay or said audio frequency energy transmission channel tosaid local voice modulation circuit.

CARL P. CLARE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,250,950 Goldsmith July 29, 19412,064,958 Taylor et al. Dec. 22, 1936 1,945,082 Sandeman et al. Jan. 30,1934

